Supranuclear Palsy, Progressive

PERK-opathies: An Endoplasmic Reticulum Stress Mechanism Underlying Neurodegeneration

The unfolded protein response (UPR) plays a vital role in maintaining cell homeostasis as a consequence of endoplasmic reticulum (ER) stress. However, prolonged UPR activity leads to cell death. This time-dependent dual functionality of the UPR represents the adaptive and cytotoxic pathways that result from ER stress. Chronic UPR activation in systemic and neurodegenerative diseases has been identified as an early sign of cellular dyshomeostasis.

The Protein Kinase R-like ER Kinase (PERK) pathway is one of three major branches in the UPR, and it is the only one to modulate protein synthesis as an adaptive response. The specific identification of prolonged PERK activity has been correlated with the progression of disorders such as diabetes, Alzheimer’s disease, and cancer, suggesting that PERK plays a role in the pathology of these disorders. For the first time, the term “PERK-opathies” is used to group these diseases in which PERK mediates detriment to the cell culminating in chronic disorders. This article reviews the literature documenting links between systemic disorders with the UPR, but with a specific emphasis on the PERK pathway. Then, articles reporting links between the UPR, and more specifically PERK, and neurodegenerative disorders are presented. Finally, a therapeutic perspective is discussed, where PERK interventions could be potential remedies for cellular dysfunction in chronic neurodegenerative disorders.

Progressive Supranuclear Palsy: What Do We Know About it?

Progressive supranuclear palsy (PSP) is a progressive tauopathy characterized by supranuclear ophthalmoplegia, pseudobulbar palsy, dysarthria, axial rigidity, frontal lobe dysfunction, and dementia. The typical pathology includes neuronal loss, gliosis and microtubule-associated protein tau (MAPT)-positive inclusions in neurons and glial cells, primarily in basal ganglia, brainstem and cerebellum. The pathogenesis of PSP is not yet completely understood; however, there are several hypotheses. This article reviews the present knowledge about PSP, and the concepts underlying mitochondrial dysfunction, lipoperoxidation, and gene mutations. The clinical features of PSP are also discussed; these include vertical gaze palsy, pseudobulbar palsy, aphasia, dysarthria, axial rigidity, and neuropsychiatric symptoms, such as amnesia, irritability, loss of interest, and dementia. In terms of diagnosis, there is considerable interest in neuroimaging for detecting PSP; therefore, neuroimaging techniques such as magnetic resonance imaging (MRI) and [18F]- fluorodeoxyglucose positron-emission tomography (FDG-PET) are reviewed. A definitive diagnosis of PSP depends on pathology, and the introduction of new clinical subtypes challenges presents the widely adopted diagnosis criteria. PSP treatments such as serotonin antagonists, α2 receptor antagonists, and coenzyme Q10 are also discussed. There is no curative therapy for PSP; all of the available treatments are palliative.

Genetic Bases of Progressive Supranuclear Palsy: The MAPT Tau Disease

Progressive Supranuclear Palsy (PSP) is a progressive neurodegenerative syndrome characterized by supranuclear palsy, postural instability, and mild dementia. Neuropathologically, PSP is a four-repeat tauopathy, defined by the accumulation of neurofibrillary tangles and tufted astrocytes. Etiology remains elusive, but genetic background has a key-role in the disease pathogenesis. Recent studies have reported high familial aggregation in PSP patients, and it has been widely demonstrated that Microtuble Associated Protein Tau (MAPT) gene mutations are causative of monogenic autosomal dominant PSP. In sporadic cases, genetic advances have further confirmed the role of MAPT in increasing disease risk, and the H1 MAPT haplotype has been consistently associated with PSP, while the H2 haplotype seems protective. Conversely, no major environmental risk factors have been reported so far. A proper evaluation of known susceptibility factors related to PSP pathogenesis may help in defining neuroprotective therapeutic approaches.

Zolpidem Therapy for Movement Disorders

Zolpidem is a selective agonist of the benzodiazepine subtype receptor BZ1. The highest density of this receptor is in the output structures of the basal ganglia. The basal ganglia are pathologically involved in many movements disorders. Thus, zolpidem has accumulated attention for a possible drug to treat neurological signs and symptoms in Parkinsonian diseases. In this mini-review, I reviewed effects of zolpidem as movement disorders including Parkinsons disease, progressive supranuclear palsy, dystonia and so on. In addition, I reviewed a possible mechanism of zolpidem for movement disorders.

Protein Misfolding in Disease: Cause or Response?

Misfolding of newly formed proteins not only results in a loss of physiological function of the protein but also may lead to the intra- or extra- cellular accumulation of that protein. A number of diseases have been shown to be characterised by the accumulation of misfolded proteins, notable examples being Alzheimers disease and the tauopathies. The obvious inference is that these proteinaceous deposits are pathogenic features of the disease. However, systems such as the unfolded protein response and ubiquitin-proteasome complex are in place in the cell to target misfolded proteins for degradation and clearance. Evidence suggests that in disease states, these protein-handling systems may be overwhelmed and the misfolded proteins accumulate as either extracellular deposits (eg. senile plaques in Alzheimers disease) or intracellular inclusions (as in Lewy bodies in Parkinsons disease). These accumulations may be the direct cause of the particular pathology associated with the diseases or they may be inert “packages” designed to protect the cell from toxic insult.